Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$152.37	5.150%	$160.2171	$160.22	$160.20	$160.20
Purchase #2	$180.38	13.516%	$204.7602	$204.76	$204.75	$204.80
Purchase #3	$170.57	11.444%	$190.09	$190.09	$190.10	$190.10
Purchase #4	$158.26	4.229%	$164.9528	$164.95	$164.95	$165.00
Purchase #5	$179.34	4.626%	$187.6363	$187.64	$187.65	$187.60
Purchase #6	$128.47	6.374%	$136.6587	$136.66	$136.65	$136.70
Purchase #7	$136.34	11.783%	$152.4049	$152.40	$152.40	$152.40
7 purchase totals =	$1,105.73		$1,196.7200	$1,196.72	$1,196.70	$1,196.80